Electric switch



Dec. 7, 1954 w. B. ELLWOOD 2,696,543

ELECTRIC SWITCH Original Filed Dec. 18, 1948 2 Sheets-Sheet 1 FIG. F/GZZ5 7 a s? u U as u u WEELLWOOD 42 BY WQM /N VENTOR ATTORNEY Dec. 7, 1954w ELLWQQD 2,696,543

ELECTRIC SWITCH Original Filed Dec. 18, 1948 2 Sheets-Sheet 2 FIG. 5

//v VEN 70/? W. B. ELLWOOD mwCm ATTORNEY United States Patent ELECTRICSWITCH Original application December 18, 1948, Serial No.

66,084, now Patent No. 2,648,167, dated August 11, 1953. Divided andthis application November 8, 1952, Serial No. 319,483

Claims. (Cl. 200-144) This invention relates to switches, and moreparticularly'to dry reed switches which can be readily andpreciselymanufactured.

.An object of the invention is to provide an inexpensive switch ofthe-dry reedtype that has a definite and preascertainable gap betweenits electrodes.

Anotheriobject of this invention is to produce a switch with a gapbetweenthe electrodes thereof that .is readily .reproducible in othersuch switches on a mass-production basis.

A feature of the invention resides in using an envelope and .a pair ofresilient electrodesone end of each being supported at opposite .ends ofthe envelope while their other ends overlap within the envelope andinclude contact surfaces which are, at the sametime, alwaysoblique to.thetline between endsof the envelope and parallel to each other, andwhich other ends are biased to abut opposite inner surfaces of theenvelope so that the gap between the contact areas of the electrodes isdependent simply upon the longitudinal displacement of the electrodesalong the line joining the ends of the envelope while the mating endsthereof are abutting the opposite inner surfaces of the envelope.

There has been difliculty in the past in manufacturing dry reed switcheswith a high degree of uniformity. This difficulty is overcome and theobjects of the in vention attained if the switch which is manufacturedcomprises an envelope wherein two electrodes areplaced substantiallyend-to-end in a longitudinal manner with respect to each other, with thecontact ends of said electrodes being beveled to form surface contactareas that are parallel to one another. It is particularly important forobvious electrical reasons that they be essentially parallel whenmating. Small variations from parallelism isnot harmful. With such aswitch configuration the gap between the two beveled contact surfacesmay be accurately and uniformly determined by inserting the switchelectrodes into opposite ends of the envelope and pushing them towardsone another until the beveled edges of the electrodes engage and thesides of thezelectrodes opposite the beveled edges abut the sides oftheenvelope, by influencing'the electrodes to produce acrepelling forcebetween them, and by then separating the electrodes longitudinally by acontrolled amout. These acts are accomplished, for example, by means ofa machine which comprises a temperature-responsive jig which holds theswitches while the elcectrodes are spaced and the switch envelope issealed in a furnace. A belt guide may be used to carry a series of theseswitch-holding jigs into a temperature-controlled furnace where thespacing and sealing steps occur. A suitable machine is disclosed herein,and is also disclosed and claimed in my Patent 2,648,167, dated August11, 1953, which was issued from the parent application of which thisapplication is a division.

The invention, the attainment of its objects, and the nature thereof,may be more fully understood from the following detailed description,when read in conjunction with the accompanying drawings in which:

.Fig. 1 shows a front view in section of an assembled switch in aninoperated or open condition with the electrodesseparated from eachother;

Fig. 2 shows a partially broken away top view of the jig which holds theswitches during the electrode-spacing and envelope-sealing steps;

Fig. 3 shows a section view of the jig taken through 3-3 of Fig. 2,showing the electrodes .of the switch fully inserted into the envelope;

Fig. 4 shows a view of a belt guide carrying a plurality of jigsidentical in structure to the jig of :Fig. 2 into a furnace where thespacing of the switch electrodes and the sealing of theswitch envelopesare accomplished;

Fig. 5 shows a partially broken away side view of the jig of Fig. 2; and

Fig. :6 shows a perspective view of the jig of Fig.2.

In Fig. 1 of the drawings, the two electrodes 7 and-8 of a complete butunoperated switch are enclosedin the tubular envelope 9 which maybeglass or other suitable material. In an exemplary embodiment electrodes7'and 8 are made of a nickel-iron alloy consisting of about fifty-oneper cent nickel and forty-nine per cent iron which has very nearly thesame coefiicientof expansion as that of the annular glass seals 10 and11. his to be noted, however, that any electrical conductingmaterialpossessing magnetic properties may beused as electrodes. The contacttips or mating ends 12 and 13 of electrodes 7 and 8, respectively, areplated with a metal which assures hard,.long wearing, low resistancecontact surfaces. Rhodium is suitable although other metals can beemployed. Each of the two electrodes 7 and 8 .is provided with an upsetflange 14 and 15, respectively. These upset flanges center theelectrodes in the glass tub during the sealing process. ,They alsodefine the cantilever length and serve as location stops for the annularglass seals 10 and 11. The contact surfaces of the electrodes-arebeveled in such a manner that the two surfaces lie in planesapproximately parallel to .each other, thus providing for good contactwhen the relay is actuated. While these beveled edges are shown parallelat all times such as merely the preferred arrangement involvingsymmetrically arranged electrodes. Parallelism when mating is the onlyessential electrical requisite. Small variations of parallelism due to.using non-symmetrical electrodes and due to usual manufacturingtolerances, etc. can be tolerated without going beyond the scope andspirit of the invention, as will be apparent to those skilled in theart. The annular glass seals 10 and 11, which are inserted in envelope 9before the spacing and sealing steps occur, have a very :low meltingpoint so as to reduce the furnace temperature required for sealing theenvelope. The seals should preferably have the same coefiicient ofexpansion as the glass envelope 9 and as the metallic electrodes 7 and8, otherwise the seals are apt to crack under the.unequal stressesimposed upon them when the switch is subjected to temperaturevariations. The melting point of the glass seals should be below thesoftening point of .the glass envelope so that the cylindrical form ofthe envelope will not be materially changed during the sealing process.As is represented by the wire .16, the assembled switch is adapted foruse in conjunction with a coil or other source of magnetic flux to forman electromagnetic relay.

In Figs. 2 and 3 of the drawings, the assembled switches'30 arepositioned in the V grooves of V-block 31 of the jig. Pole-pieces 17,18, 19, 17A, 18A and 19A, which are constructed of magnetic material,cooperate with permanent magnets 27 and 27A (Fig. 3) to constitute twomagnetic chucks which grip the electrodesof each switch. These chucksare firmly atfixed to end piece 21 and frame 20, respectively, so thatthe electrodes are held in a fixed position with respect to frame 20 andend piece 21, respectively. .As will be seen in Fig. 3, one of theelectrodes for each switch abuts polepiece 17A, which aids in properlypositioning the electrodes prior to the spacing and sealing of theelectrodes within a furnace.

In an exemplary embodiment of the invention, bimetal washers 22 and 22Aare placed on support rods 23 and 23A, respectively, one end of each ofthe rods 23 and 23A being permanently attached to frame 20, the otherend of each of the rods being frictionally engaged by end piece 21. Whenthe jig is heated in a furnace the bimetal washers expand and the depthof the cone formed by washers 22 and 22A increases, thereby forcing endpiece 21 away from frame 20. End piece 21 is held in this displacedposition when the jig is cooled and the washers return to their normaldimensions by virtue of the frictional engagement between the rods 23and 23A and the end piece 21. Thus, the electrode spacing created by thewasher expansion is maintained. Spring clamp holder 24, which maintainsthe switch envelopes in position, is held in place by screws 25 and 25Awhich are inserted in common supports 26 and 26A. Frame 20, end piece21, and support rods 23 and 23A are all made of non-magnetic material.

Magnets 27 and 27A are composed of a magnetic material which will retainits permanent magnet prop erties to a high degree at temperatures inexcess of 500 C.; for example, a material of this type which is suitableis disclosed in Kelsall et al. United States Patent 2,190,667, datedFebruary 20, 1940, as containing 29 per cent nickel, 50 per cent ironand 13 per cent aluminum, although other alloys of suitable propertiesare also known in the prior art.

Metallic pieces 28 and 28A are fabricated from nonmagnetic materialsince their function is to support pole pieces 17, 18 and 19 and 17A,18A and 19A, respectively, without shorting the magnetic circuits. Topclamp plates 29 and 29A, which are constructed of magnetic material, arelaid on the top of the projecting extremities of the switch electrodesso as to reduce the reluctance of the magnetic path for the magneticchucks, as is best shown in Figs. and 6. V-block 31 is fimly supportedby and fastened to block 32, the combination of which is secured toframe 20. Fastened to spring clamp holder 24 by rivets 34 is a series ofspring clamps 33, one for. each switch being manufactured. These springclamps help to hold the glass envelopes in a fixed position during thespacing and sealing steps.

In Fig. 4, jigs 35, which hold the switches to be spaced and sealed, arecarried through heater furnace 36 on conveyor belt 37. Regularly spacedon the conveyor belt 37 are stops 38 designed to hold and position jigs35 as they pass through tube 43 and furnace 36. The conveyor belt isguided and driven by pulleys 39, 57 and 58. An idle pulley 41 and spring40 with a weight 42 attached to said spring 40 is provided to maintain adesired tension in the conveyor belt. The conveyor belt 37 passesthrough the cylindrical metal tube 43 which has an extension 44 leadingto a supply of helium orany other type gas with which it is desired tofill the glass envelopes of the switches. Also attached to metal tube 43are flexible flaps 45, 46, 47, 48, 49 and 5d, preferably made of asilicone rubber although other suitable heat resistant materialsimpermeable to gases may be used. These flexible flaps help to preventair contamination of the helium or other gas injected into the metaltube 43. The purpose of injecting this gas into the metal tube 43 is toallow the unsealed envelopes of the switches to become filled with theinjected gas by diffusion before the ends of the glass envelope aresealed in heater furnace 36. At both ends of the conveyor belt areplatforms, platform 51 being designated as the entrance platform andplatform 52 as the exit platform. The loaded jigs are manually placed onthe conveyor belt and automatically leave the conveyor belt and restupon exit platform 52.

The method of manufacture will now be described in detail. Each switchis assembled by placing two electrodes having a structure identical tothat of electrodes 7 or 8 (Fig. l) in a glass envelope such as envelope9. The beveled surfaces of these electrodes are forced against oneanother in a manner shown in the broken section 59 of Fig. 3. Annularglass seals such as and 11 are inserted over the projecting extremitiesof the electrodes until they rest on the upset flanges 14 and 15,respectively. The assembled switches are then placed in the jig in amanner which is best shown in Fig. 6. In particular, the assembledswitches rest in the V grooves of block 31. The electrodes at the sameend of each switch rest against pole-piece 17A as is shown in Fig. 3.The magnetic top plates 29 and 29A rest on top of the projectingextremities of the electrodes. To make sure the electrodes arepositioned so that their contact surfaces are touching each other andthe side of each electrode opposite the beveled surface is in con tactwith the inner wall of the glass envelope as is shown in the brokensection 59, each electrode end exposed by aperture 60 can be tappedlightly. The electrodes are held in a fixed position with respect toframe 20, end piece 21 and the magnetic chucks by the forces exerted bythe magnetic lines of force 61 and 62 shown in Fig. 3. Positioned asshown in Fig. 1 the glass seals 10 and 11 will melt when subjected tothe heat of the furnace and upon cooling will form a seal. The jigs aremoved from the entrance platform 51 so as to approach the furnace 36through tube 43, the glass envelopes are filled with helium bydiffusion, and by the time the seals are made, the glass envelopescontain helium of sulficient purity for useful operation of saidswitches. As the switches are subjected to heat the bimetal washers 22and 22A expand and push end piece 21 and its associated magnetic chuckaway from frame 20. Since the magnetic chuck is fastened securely to endpiece 21, the electrodes of each switch are pulley apart a certain fixedand uniform longitudinal distance which is dependent upon thecoefficient of expansion of the bimetal washeig and their temperature.There is a friction surface between support rods 23 and 23A and endpiece 21 so that upon cooling, the end piece 21 does not return to itsoriginal position, but remains in the position it was in during theheating period. Thus, the gap between the electrodes is a reproducibleone since the temperature is controllable. It should be noted here thatthe polarity of magnets 27 and 27A should be arranged so that thecontact ends of the electrodes are of the same magnetic polarity andthus will repel each other as one is drawn away from the other duringthe manufacturing process. This keeps the electrodes in continuouscontact with the inner surfaces of the glass tubes during the entiremanufacturing process, which insures a uniform, reproducible gap betweensaid electrodes.

It is to be understood that the above description is an exemplaryembodiment of the invention and that other materials, elements, andarrangements may be utilized without departing from the spirit and scopeof the invention.

What is claimed is:

1. In a switch, a tubular envelope having a longitudinal axis, and apair of electrodes affixed at one end to and extending longitudinallywithin said envelope, each electrode having a surface contact area onits other end capable of mating with the contact area of the otherelectrode, said mating ends of said electrodes normally engaging theopposite inner sides of said envelope and displaced with respect to eachother along said axis so as to overlap one another to provide apredetermined gap between said contact surfaces, said mating surfaces ofsaid electrodes being at all times oblique to said longitudinal axis andbeing parallel to one another.

2. In a switch, an envelope, a pair of displaceable electrodes one endof each being supported at opposite ends of said envelope andoverlapping each other at their outer ends within said envelope, saidother ends having cooperating parallel contact areas always oblique tothe axis joining the ends of said envelope, said other ends biased toabut opposite inside surfaces of said euvelope and disposed with respectto each other along said axis of said envelope to define a predeterminedgap between the contact areas thereof.

3. In a switch, an envelope, a pair of displaceable electrodes one endof each being supported at opposite longitudinal ends of said envelopeand overlapping each other at their other ends within said envelope,said other ends having cooperating parallel beveled contact areas alwaysoblique to the longitudinal axis of said envelope, said other endsbiased to abut opposite inside surfaces of said envelope and disposedwith respect to each other along the longitudinal axis of said envelopeto define a predetermined gap between the contact areas thereof.

4. In a switch, an elongated gnvelope, a pair of magnetically responsiveelectrodes one end of each being supported at respective ends of saidenvelope and overlapping each other at their other ends within saidenvelope, said other ends having cooperating parallel beveled contactareas always oblique to the longitudinal axis of said envelope, saidother ends biased to abut opposite inside surfaces of said envelope anddisposed with respect to each other along the longitudinal axis of saidenvelope to define a predetermined gap between the contact areasthereof.

5. In a switch, a hermetically sealed elongated tubular envelope, a pairof magnetically responsive rod-like electrodes one end of each beingfixed to respective ends of said envelope and overlapping each other attheir other ends within said envelope, said other ends having beveledcontact tips comprising facing parallel contact areas always oblique tothe longitudinal axis of said envelope, said tips biased so that thesides of said tips opposite said contact areas abut opposite insidesurfaces of said envelope and disposed with respect. to each other alongthe longitudinal axis of said envelope to define a predetermined gapbetween the contact areas thereof.

References Cited in the file of this patent Number 5 1,879,131 2,264,7462,506,414 2,586,309

Number UNITED STATES PATENTS Name Date Dobke Sept. 27, 1932 Ellwood Dec.2, 1941 Ellwood May 2, 1950 Dales Feb. 19, 1952 FOREIGN PATENTS CountryDate Great Britain Oct. 11, 1928

